Are there EWSR1 rearranged cutaneous hidradenomas and mucoepidermoid carcinomas of salivary glands? A FISH study and review of the literature

MAML2 rearrangements have been previously described for hidradenomas and muco-epidermoid carcinomas (MEC). However, one report showed EWSR1 rearrangement in both tumours. In this study, EWSR1 and MAML2 translocation were investigated in hidradenomas and MECs. Specimens from thirteen MECs of the salivary glands and twenty hidradenomas of the skin were evaluated. Fluorescence in situ hybridisation (FISH) studies with EWSR1 and MAML2 break-apart probes were used. Forty percent of hidradenomas and 84.6% of MECs showed a positive MAML2 break signal. EWSR1 break signal was absent in hidradenomas. Only two MECs showed positive EWSR1 signal and were, thus, reclassified as clear cell carcinoma (CCC). A statistically significant relationship was also observed between clear cells containing hidradenomas and the FISH status. Despite the previous study, EWSR1 translocations could not be established in hidradenomas and MECs. The study further suggests that evaluation of EWSR1 might be obligatory for the correct diagnosis of MAML2-negative MECs to exclude the chance of CCCs. The present study also supports the notion that MAML2 can be used as a marker for hidradenomas and MECs